Control systems for mechanical respirators



June 5, 1962 w. H. SMITH 3,037,498

CONTROL SYSTEMS FOR MECHANICAL RESPIRATORS Filed Aug. 29, 1957 2 SheetSSheet l 36 I 2 3 g a1 2 l5 IO a I I 8 .& t&\\\\\\\ 23 8 3 2 u I4 22 FIG2 no.3

INVENTOR.

- WILLIAM HAROLD SMITH June 5, 1962 w. H. SMITH CONTROL SYSTEMS FORMECHANICAL RESPIRATORS Filed Aug- 29; 1957 2 Sheets-Sheet 2 3,037,498Patented June 5, 1962 3,037,498 CONTROL SYSTEMS FOR MECHANICALRESPIRATORS William Harold Smith, Norwalk, Conn., assignor, by

mesne assignments, to Shampaine Industries Inc.,

St. Louis, Mo., a corporation of Missouri Filed Aug. 29, 1957, Ser. No.681,115 15 Claims. (Cl. 12830) This invention relates in general tomedico-electronic devices and, more particularly, to a control systemfor mechanical respirators, such as iron lungs and the like.

In the care of patients sufiering from poliomyelitis affecting thethoracic muscles, normal breathing is usually impossible. Such patientscan be sustained, however, through resort to artificial breathingdevices, such as the so-called iron lung or similar equipment in whichmotor driven pumps alternately apply increasing and decreasing pressurewithin the chamber surrounding the patients body or chest. When thepressure is slightly above atmospheric pressure, it is usually referredto by physicians as positive pressure and, under such pressurecondition, the patient exhales. Similarly, when the pressure is slightlybelow atmospheric, it is usually referred to as negative pressure andthe patient inhales. If a patient had a complete muscular deficiency inthe chest and had no ability whatsoever to breathe, the iron lung wouldbe substantially satisfactory. However, most patients have some residualbreathing power and it is highly desirable to stimulate the recovery, sofar as possible, of more and more independent breathing power on thepart of the patient. Moreover, Where a patient with some residualbreathing power is placed in a respirator of any type, the operationalcycle of the machine must be adjusted closely to the patients breathingcycle, but the patient also must learn to synchronize his breathing withthe cycle of the machine. Unless the timing of both machine and patientare closely observed and held in synchronized relation, the patient willsoon be trying to exhale When the machine is applying negative pressureand inhale when the machine is applying positive pressure, thereby, inextreme cases, producing suliocation and death.

Even where the situation is not severe, many polio patients are overventilated, that is to say, forced to breath too deeply and too often,thereby causing a dangerous CO level and blood pH. Another seriousdefect in mechanical respirators is the creation of an excessive andconstant negative pressure on inhalation, which eventually leads toemphysema. It, therefore, would be extremely desirable to operatemechanical breathing devices on patient demand.

Hence, it is the primary object of the present invention to providemeans and methods for synchronizing the operational cycle of mechanicalrespirators with the patents breathing cycle and maintaining suchsynchronism during any and all variations in patient-demand.

It is another object of the present invention to provide a sensingelement which responds to the flow of breath from the nose of a patient.

It is a further object of the present invention to provide a device ofthe type stated which is simple and yet highly accurate.

It is also an object of the present invention to provide a device of thetype stated which can be comfortably applied to the patient.

With the above and other objects in view, my invention resides in thenovel features of form, construction, arrangement, and combination ofparts presently described and pointed out in the claims.

In the accompanying drawings FIG. 1 is a front elevational view of therespirator control constructed in accordance with and embodying thepresent invention;

FIG. 2 is a vertical sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken along line 33 of FIG. 2;

FIG. 4 is a perspective view of the nasal sensing vane and shutterforming a part of the present invention;

FIG. 5 is a schematic wiring diagram of the control system; and

FIG. 6 is a block diagram showing the control unit and its connection toa thorax shell.

Referring now in more detail and by reference characters to thedrawings, which illustrate a preferred embodiment of the presentinvention, A designates a control system for mechanical respiratorsincluding a housing 1 comprising front and rear walls 2, 3, a bottomwall 4, end walls 5, 6, and a partition 7 intermediate the end walls 5,6. Rigidly secured to the bottom wall 4 by means of bolts 8 and betweenthe partition 7 and end wall 6 is a nasal sensory device 9 including abase mem ber 10 having a horizontal inlet conduit 11 tapped at one endfor reception of a fitting 12 secured to one end of a flexible tube 13.At its other end, the conduit 11 curves upwardly and terminates in ashoulder 14 which is presented toward a chamber 15. The base member 10is also provided with an outlet conduit 15 which terminates at its innerend in the chamber 15 in upwardly spaced relation to the shoulder 14.Positioned within the base member 10 and within the chamber 15 is a verylight weight sensing element 16 including an elongated rod 17 integrallyprovided intermediate its ends with a pair of opposed shafts 18, 18,each being rockably journaled in the base member 10. At its forward end,

the rod 17 is provided with a thin flat shutter 19 and at its rear endthe rod 17 is provided with a [flat vane 20 lying in a plane at rightangles to, and being slightly heavier than, the shutter 19 so as tonormally bear against the shoulder 14 closurewise across the conduit 11.Bored through the base member 10 are spaced aligned apertures 21, 22,each of which communicates with the chamber 15. Also mounted within thehousing 1 adjacent the aperture 21 is an illumination source 23 andsimilarly mounted adjacent the aperture 22 is a photoelectric cell 24.The photoelectric cell 24 is of the cadmium sulphide type and isphoto-resistive so that as the light intensity on the photo-sensitivearea of the cell 24 increases, the resistance of the cell 24 decreases.It will be apparent that when the sensing element 16 is in the positionshown in full lines in FIG. 3, the shutter 19' will prevent the lightfrom the illumination source 23 from impinging upon the photoelectriccell 24, but when the sensing element 16 is in the position shown indotted lines, the light will be directed through the apertures 20, 21,so as to strike the photoelectric cell 24.

The control circuit for the device A includes a selenium rectifier :25,a fixed resistor 26, an electrolytic capacitor 27, a S.P.S.T. relay 28having contacts 29, 29, a power on-oif switch 30, power on-ofi pilotlight 31, and a switch 32 for starting a motor 33. Also included in thecircuit is a S.P.D.T. time delay relay 34 having contacts 35, 35, 36, amanually operable S.P.D.T. selector switch 37 having contacts 38, 38',39, a D.P.D.T. latching relay 40 having contacts 41, 41', 42, 42', 43,an inspiration coil 44 and an expiration coil 45, an expiration timer 46including a motor 47 adapted to open and close contacts 48, 48', aninspiration timer 49 including a motor 50 adapted to open and closecontacts 51, '51, and a solenoid operated sequencing valve 52 having asolenoid 52. Preferably, the circuit is also provided with an expirationpilot light 53 and an inspiration pilot light 54, each of which isilluminated when the timer associated therewith is in operation. Theexpiration timer 46 and inspiration timer 49 are of similar constructionand each may be set to operate for a predetermined period of time, atthe end of which the contacts therein will be momentarily closed and forpurposes presently more fully appearing. The aforementioned circuitcomponents are connected together in the manner shown in FIG. 5.

The solenoid sequencing valve 52 is interposed between a conventionalpneumatic thorax shell 55 and pump 56, which is, in turn, operativelyconnected to the motor 33, as shown in FIG. 6, so that the valve 52 cancontrol the application of either positive or negative pressure in thethorax shell 55. Thus, when the solenoid 52 is energized, the valve 52opens, applying positive pressure to the thorax shell 55, and, when thesolenoid 52 is de-energized, the valve 52 will permit the application ofnegative pressure in the thorax shell 55. The motor 33, pump 56,solenoid operated valve 52, and thorax shell 55 are all normally mountedon a mechanical respirator diagrammatically indicated at 57, the detailsof which are conventional and are, therefore, not shown or described.With the exception of the motor 33 and solenoid operated valve 52, thecomponents of the circuit shown in FIG. 5 are all mounted in the housing1 and an electrical cable 58 is provided for connection between thehousing 1 and the respirator 57. For convenience, the switches 30, 32,37, and the pilot lights 31, 53, 54, are mounted on the front wall 2 ofthe housing 1, as shown in FIG. 1.

In use, the free end of the tube 13 is preferably taped or otherwisesecured adjacent the patients nostrils and the switch 30 is closed,illuminating the pilot light 31. If it is desired to provide timedrespiration, the switch 39 is manually moved to the Timed position toclose the contacts 38, 39, as shown in full lines in FIG. 5. The switch32 is then closed to start the operation of the motor 33. Initially, thecontacts 42', 43, of the latching relay 40 are closed, as shown in fulllines, allowing current to flow through the inspiration pilot light 54and also through the inspiration timer motor 50. The solenoid 52' isde-energized so that the valve 52 will cause negative pressure to beapplied to the patient through the thorax shell 55. The inspirationtimer motor 50 will operate for its pre-selected period of time, at theend of which time there will be a momentary closing of contacts 51, 51',allowing current to flow through the expiration coil 45 of the latchingrelay 40, causing the contacts 41', 42, and the contacts 41, 42', in thelatching relay 40 to close and lock. At the same time, current will alsofiow through the expiration pilot light 53, the expiration timer motor47, and through the solenoid 52', energizing same and opening the valve52 so as to apply positive pressure from the pump 56 to the thorax shell55.

The expiration timer motor 47 will operate throughout its pro-selectedtime, at the end of which time there will be a momentary closing of thecontacts 48, 48', permitting current to flow through the inspirationcoil 44 of the latching relay 40, opening the contacts 41', 42, and thecontacts 41, 42, and closing the contacts 42, 43. When the contacts 41,42, open, the solenoid 52' is de-energized, closing the valve 52,thereby applying negative pressure to the thorax shell 55, completingthe cycle. It should be noted that when the selector switch 39 is set tothe Timed position, there will be no current flowing through the lamp 23or photoelectric cell 24 and the breathing of the patient is completelycontrolled by the operational cycle of the control circuit.

When it is desired to adjust the operation of the thorax shell 55 inaccordance with the residual breathing power of the patient, theselector switch 39 is manually moved to the Demand position, closingcontacts 38, 39; whereupon, the inspiration timer motor 50 is cut out ofthe circuit and current is supplied to the illumination source 23 andphotoelectric cell 24. The solenoid 52 in the valve 52 will bede-energized and negative pressure will be present in the thorax shell55. The contacts 42', 43, of the latching relay 40 will be closed andcurrent will flow through the inspiration pilot light 54, and as long asthe patient is inhaling, the circuit will remain locked in thisposition. When the patient exhales, a slight amount of pressure is builtup in the tube 13 and inlet conduit 1-1, which is impressed upon thevane 20, causing the sensing element 16 to swing to the position shownin dotted lines in FIG. 3 and move the shutter 19 out from between theapertures 21, 22. Light from the illumination source 23 will thenimpinge upon the photoelectric cell 24, decreasing its resistance andallowing current to fiow therethrough and through the relay 28, closingits contacts 29, 29. As soon as the contacts 29, 29, of the relay 28 areclosed, current will flow through the time delay relay 34, the contacts35, 36, of which are normally closed as shown in full lines. Currentalso will flow through the expiration coil 45, closing the contacts 41',42, and 41, 42', through the expiration timer motor 50, and through thesolenoid 52, which opens the valve 52, causing positive pressure to beapplied from the pump 56 to the thorax shell 55. The expiration timermotor 50 will operate throughout its pre-selected period of time, at theend of which time there will be a momentary closing of the contacts 48,48', allowing current to flow through the inspiration coil 44, causingthe contacts 41, 42, and 41, 42, to open, and causing the contacts 42,43, to close. When the patient has finished exhaling, the sensingelement 16 returns to the position shown in full lines in FIG. 3,causing the shutter 19 to prevent light from striking the photoelectriccell 24; whereupon, the contacts 29, 29', in the re lay 28 will open,stopping current flow through the relay 34 and closing the contacts 35,36, therein. At the moment the relay 28 closed, allowing current to flowthrough the time delay relay 34, the contacts 35, 36, remained closedfor a delay period of about one second, at the end of which time thecontacts 35, 36, were opened and the contacts 35', 36, were closed,causing the contacts 51, 51', of the inspiration timer motor 49 to beclosed. Therefore, if, for some reason or another, the sensing element16 should become stuck in the position shown in dotted lines in 'FIG. 3,allowing light to continuously impinge upon the photoelectric cell 24,the relay 34 acts as a safety device preventing the thorax shell 55 frombeing continuously held in the expiratory position, since failure of thecontacts 35, 36, of the relay 34 to open will cause the circuit to belocked into timed respiration.

It will be apparent that by setting the selector switch 39 to operate ondemand respiration, the device A can synchronize the operation of therespirator 57 in accordance with the patients need to exhale, althoughthe length of time through which the thorax shell 55 operates to applypositive pressure is timed.

It should be understood that changes and modifications in the form,construction, arrangement, and combination of the several parts of thecontrol systems for mechanical respirators may be made and substitutedfor those herein shown and described without departing from the natureand principle of my invention.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising thorax-constricting means for alternately increasing anddecreasing the pressure on the chest of the patient,current-transmitting means operatively associated with saidthorax-constricting means, and a nasal sensing device including asensing element movably secured therein, said sensing element beingprovided with a pressure-responsive element the actuation of which willmove said sensing element, said sensing element being operativelyassociated with and adapted to actuate said current-transmitting meansso that movement of said sensing element will determine the point intime at which the applied pressure on the chest of the patient increasesand decreases.

2. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately increasing and decreasing the pressureon the chest of the patient, current transmitting means operativelyassociated with said last-mentioned means, said current transmittingmeans being adapted to control the point in time at which the appliedpressure on the chest of the patient increases, a nasal sensing elementoperatively associated with and adapted to actuate said currenttransmitting means, and means by which the nasal sensing element can beoperatively connected to the nostrils of the patient so as to beresponsive to the residual breathing cycle of the patient.

3. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately increasing and decreasing the pressureon the chest of the patient, a photo-electric cell, an illuminationsource adapted to direct light onto said photo-electric cell, saidaforementioned means being operatively associated with and responsive tothe current flow through the photoelectric cell, the current flowthrough said photo-electric cell being adapted to control the point intime at which the applied pressure on the chest of the patient increasesand decreases, a movable sensing element having a shutter for optionaldisposition across the beam of light from the illumination source,whereby to control the current flow through the photo-electric cell, andmeans by which the sensing element can be operatively connected to thenostrils of the patient so as to be movable responsive to the residualbreathing cycle of the patient.

4. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately increasing and decreasing the pressureon the chest of the patient, a photo-electric cell, an illuminationsource adapted to direct light onto said photo-electric cell, saidaforementioned means being operatively associated with and responsive tothe current flow through the photo-electric cell, the current flowthrough said photo-electric cell being adapted to control the point intime at which the applied pressure on the chest of the patient increasesand decreases, a movable sensing element having a shutter for optionaldisposition across the beam of light from the illumination source,whereby to control the current flow through the photo-electric cell,said sensing element also being provided with pressure-responsive meansoperatively connected to said shutter, and means by which thepressure-responsive means can be operatively connected to the nostrilsof the patient so as to be actuable responsive to the residual breathingcycle of the patient.

5. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately increasing and decreasing the pressureon the chest of the patient, a photo-electric cell, an illuminationsource adapted to direct light onto said photo-electric cell, saidaforementioned means being operatively associated with and responsive tothe current flow through the photo-electric cell, the current flowthrough said photo-electric cell being adapted to control the point intime at whichthe applied pressure on the chest of the patient increasesand decreases, a movable beam-like member provided with a shutter foroptional disposition across the beam of light from said illuminationsource, whereby to control the current flow through the photo-electriccell, pressure-responsive means mounted on said beam-like element andbeing slightly heavier than said shutter, and means by which thepressure-responsive means can be operatively connected to the nostrilsof the patient so as to be actuable responsive to the residual breathingcycle of the patient.

6. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of a patient in synchronized relation with thepatients breathing and control means including photoelectric cell meansand a movable sensing element operatively connected to saidphotoelectric cell means, said control means operatively associated Withsaid last-mentioned means and being operable to apply increasingpressure on the chest of the patient throughout a preselected timeinterval commencing upon exhalation by the patient.

7. A nasal sensory device comprising a base member having a conduittherein, said base member furthermore being provided with a chamberadapted to communicate with said conduit, means for connecting saidchamber to the nose of a patient along a path which includes saidconduit, an elongated beam-like member operatively mounted in saidchamber and being provided with a vane adapted for normal dispositionclosurewise across said conduit, and a shutter operatively mounted onsaid elongated beam-like member, photoelectric cell means operativelyassociated with said base member, said vane being movable when pressureis created in said inlet conduit and thereby move said shutter so thatsaid photoelectric cell means can be actuated.

8. A nasal sensory device including a base member having a chamber,inlet and outlet conduits each communicating with the chamber, means forconnecting said chamber to the nose of a patient along a path which includes the inlet conduit, and a sensing element rockably mounted in saidchamber and being provided with a vane adapted for normal dispositionclosurewise across said inlet conduit, said sensing element furthermorebeing provided with a shutter, photo-electric cell means operativelyassociated with said sensing element, said vane being movable whenpressure is created in said inlet conduit and thereby move said shutterso that said photoelectric cell means can be actuated.

9. A nasal sensory device comprising a base member provided with achamber, inlet and outlet conduits formed in said base member andcommunicating with said chamber, said base member also having aperturescommunicating with said chamber, an illumination source andphotoelectric cell each operatively associated with said base member andbeing so arranged that a beam of light from said illumination sourcewill pass through said apertures and chamber and impinge upon thephoto-electric cell, and a sensing element operatively mounted in saidchamber and being provided with a shutter adapted for optionaldisposition in said beam of light, said sensing element also beingprovided with means for normally closing off said inlet conduit whensaid shutter is away from said beam of light, said last-mentioned meansalso being actuable to open said inlet conduit and simultaneously movethe shutter to a position in said beam of light.

10. Apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of the patient, control means operativelyassociated with said last-mentioned means for operating saidlast-mentioned means and thereby apply increasing pressure on the chestof the patient throughout a preselected time interval, and nasal sensingmeans adapted for operative connection to the nostrils of the patientand also operatively associated with said control means, said nasalsensing means being operable to actuate said control means and causesaid increasing pressure to be applied to the chest of the patientthroughout said preselected time interval commencing upon exhalation ofthe patient.

11. Apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of the patient, control means operativelyassociated with said last-mentioned means for operating saidlast-mentioned means and thereby apply increasing pressure on the chestof the patient throughout a preselected time interval, nasal sensingmeans adapted for operative con nection to the nostrils of the patientand also operatively associated with said control means, said nasalsensing means being operable to actuate said control means and causesaid increasing pressure to be applied to the chest of the patientthroughout said preselected time interval commencing upon exhalation ofthe patient, said nasal sensing means also being operable to releasesaid increased pressure at the end of said preselected time interval,and means for releasing said pressure upon failure of said nasal sensingmeans to cause release of said pressure.

12. Apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of the patient, current-transmitting meansoperatively associated with said last-mentioned means for operating saidlast-mentioned means and thereby applying increasing pressure on thechest of the patient throughout a preselected time interval, and nasalsensing means adapted for operative connection to the nostrils of thepatient and also operatively associated with said currenttransmittingmeans, said nasal sensing means being operable to actuate saidcurrent-transmitting means and cause said increasing pressure to beapplied to the chest of the patient throughout said preselected timeinterval commencing upon exhalation of the patient.

13. Apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of the patient, control means operativelyassociated with said last-mentioned means for operating saidlastmentioned means and thereby apply increasing pressure on the chestof the patient throughout a preselected time interval, nasal sensingmeans adapted for operative connection to the nostrils of the patientand also operatively associated with said control means, said nasalsensing means being operable to actuate said control means and causesaid increasing pressure to be applied to the chest of the patientthroughout said preselected time interval commencing upon exhalation ofthe patient, said nasal sensing means also being operable to releasesaid increased pressure at the end of said preselected time interval,and relay means operatively interposed between the current-transmittingmeans and pressure-applying means for releasing said pressure uponfailure of said nasal sensing means to cause release of said pressure.

14. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual reathing power, said apparatuscomprising thorax-constricting means, electrically operated means forcontrolling the thorax-constricting means and causing saidthorax-constricting means to apply increasing and decreasing pressurealternately on the patient, currenttransrnitting means for actuatingsaid electrically operated means, switch means operatively connectingthe current-transmitting means and electrically operated means, andnasal sensing means responsive to the residual breathing cycle of thepatient and operatively associated with and adapted to actuate thecurrent-transmitting means, thereby controlling the point in time atwhich the applied pressure on the patient increases, said switch meansbeing operable to disconnect said current-transmitting means from theelectrically operated means so that the electrically operated means cancontrol the operation of the thorax-constricting means independently ofthe nasal sensing means.

15. An apparatus for use with patients who are unable to sustain normalbreathing but have some residual breathing power, said apparatuscomprising means for alternately applying increasing and decreasingpressure on the chest of the patient for predetermined time intervals,current-transmitting means connected to and operable to actuate saidlast-mentioned means, sensing means responsive to the residual breathingcycle of the patient and operatively associated with and adapted toactuate said current-transmitting means, thereby controlling the pointin time at which applied pressure on the patient increases, and meansoperatively interposed between the current-transmitting means andpressure-applying means and being operable to break the connectionbetween the current-transmitting means and pressure-applying means,whereby the latter can operate independently of the sensing means.

References (Jited in the file of this patent UNITED STATES PATENTS2,067,744 Williams Jan. 12, 1937 2,071,215 Peterson Feb. 16, 19372,436,853 Coleman Mar. 2, 1948 2,754,819 Kirschbaum July 17, 1956FOREIGN PATENTS 528,669 Great Britain Nov. 4, 1940

